[PATCH v5] Chapter-on-need-for-RTEMS-specific-cross-compiler

[Gedare Bloom]

On Fri, Apr 3, 2020 at 11:19 AM utkarsh.rai60 at gmail.com
<utkarsh.rai60 at gmail.com> wrote:
>
> ---
>  user/start/tools.rst | 32 ++++++++++++++++++++++++++++++++
>  1 file changed, 32 insertions(+)
>
> diff --git a/user/start/tools.rst b/user/start/tools.rst
> index c3f039b..c1cd141 100644
> --- a/user/start/tools.rst
> +++ b/user/start/tools.rst
> @@ -76,3 +76,35 @@ source code used.
>
>
>  Add ``--verbose`` to the GCC command for the the verbose version details.
> +
> +Need for RTEMS-Specific Cross-Compiler
> +---------------------------------------------------------
> +
> +New users are often confused as to why they cannot use their distribution's
> +cross-compiler for their target on rtems, e.g., the riscv64-linux-gnu or the
> +arm-none-eabi-gcc on RTEMS. Below mentioned are some of the reasons for using
> +the RTEMS cross-compiler.
> +
> +* ``Correct configuration of Newlib -``
The only question I have is whether we need this ``... -`` formatting?
Does it add much value

> +     Newlib is a C standard library implementation intended for use on embedded
> +     systems. Most of the POSIX and libc support for RTEMS is derived from
> +     Newlib. The RTEMS cross-compiler configures Newlib correctly for RTEMS.
> +
> +* ``Threading in GCC support libraries -``
> +     Several threading packages in GCC such as Go threads (libgo), OpenMP
> +     (libgomp), and OpenACC need to be customized according to RTEMS. This is
> +     done by the RTEMS specific cross-compiler.
> +
> +* ``Provide preprocessor define __rtems__ -``
> +     The  ``__rtems__``  preprocessor define is used to provide conditional code
> +     compilation in source files that are shared with other projects e.g. in
> +     Newlib or imported code from FreeBSD.
> +
> +* ``Multilib variants to match the BSP -``
> +     RTEMS configures GCC to create separate runtime libraries for each
> +     supported instruction set, floating point unit, vector unit, word size
> +     (e.g. 32-bit and 64-bit), endianness, ABI, processor errata workarounds,
> +     and so on in the architecture. These libraries are termed as :ref:`Multilib
> +     <TargetArchitectures>` variants. Multilib variants to match the BSP are set
> +     by selecting a specific set of machine options using the RTEMS
> +     cross-compiler.
> --
> 2.17.1
>
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